As one of the UWB (Ultra Wide Band) technologies, the development of an equipment or system for holding communication or distance measurement by using a pulse signal is proceeding. In order to shape the pulse signal into an alternating signal that has only a component in a desired frequency band, roughly there are two methods. One is the method of limiting a frequency band of the pulse signal by a filter to extract a particular frequency band component only, and the other is the method of either extracting partially an alternating signal by placing a window intermittently on the alternating signal or operating an oscillator circuit serving as an alternating signal source intermittently to generate an oscillation itself intermittently.
As the method of multiplying the pulse signal by an alternating signal source (the method of extracting partially an alternating signal by placing a window intermittently on the alternating signal), it is common to modulate an output of the oscillator circuit and the pulse signal by using a mixer circuit, like a carrier communication. Also, as the method of operating the oscillator circuit intermittently, the method of operating the oscillator circuit intermittently by turning ON/OFF an electric current flowing through the oscillation circuit using a transistor by a switch has been proposed.
Also, the technology to operate differentially the oscillator circuit by using paired transistors is disclosed. A configuration in the technology is shown in FIG. 15. FIG. 15 is a block circuit diagram showing a configuration of the intermittent differential oscillation apparatus using the transistors in the prior art.
This oscillator circuit is constructed by a differential oscillator portion 1605 that is composed of a current source switch 1601, transistors 1602, 1603, and a resonance circuit 1604, and a first control signal generation circuit 1606. The current source switch 1601 is operated intermittently by a control signal output from the first control signal generation circuit 1606. The differential oscillator portion 1605 oscillates in response to a voltage level and an applied period of the control signal being output from the first control signal generation circuit 1606 (see Patent Literature 1).
However, in the circuit configuration in the prior art, two transistors start the operation simultaneously in starting the operation of the differential oscillator portion 1605. Therefore, an infinitesimal delay time is caused until the oscillator circuit starts its differential operation after a resonance occurs at a frequency decided by a circuit constant.
Here, when a potential difference between two output terminals is output by operating the differential oscillator portion 1605 intermittently in unit of nanosecond, waveforms that are not in an opposite phase respectively are output from two terminals at a pulse rise time of the oscillation output due to occurrence of the infinitesimal delay time. Therefore, voltage oscillations between two output terminals of the differential oscillator portion 1605 are canceled or synthesized in a condition that they are not in phase with each other, and thus a large output amplitude cannot be obtained. As a result, the rising of the oscillation output is delayed and thus, when a pulse width is given in unit of nanosecond, in some cases the differential oscillator portion 1605 cannot generate the oscillation output with an intended time width.
In order to solve this problem, a configuration shown in FIG. 14 has been proposed. FIG. 14 is a block circuit diagram showing a configuration of an intermittent differential oscillation apparatus using transistors in the prior art. This oscillator circuit includes a current source 1501, a constant-voltage power supply 1502, a resonator 1503, a resonator 1504, transistors 1505 to 1508, and a control signal input terminal 1509. In this case, the transistor 1505 and the current source 1501 connected in series perform a function of the current source switch 1601 shown in FIG. 15. That is, when the current source switch 1601 shown in FIG. 15 is operated intermittently by a control signal that controls an intermittent operation, it fulfills a function equivalent to an intermittent operation of the transistor 1505. Also, the current source switch 1601 shown in FIG. 15 performs a function of a constant-current source similar to the current source 1501 shown in FIG. 14.
The intermittent operation is made based on a rectangular wave that is input from the control signal input terminal 1509 connected to a base terminal of the transistor 1505. In this case, when the intermittent operation is turned off, no current flows through the current source 1501 and a standby current flows through inductors between the constant-voltage power supply 1502 and the resonator 1503.
Then, as soon as a rectangular wave that is input into the transistor 1505 and the intermittent operation is turned on, the standby current is cut off and a ringing is caused in the circuit through the influence of this cut-off. The oscillator circuit is operated rapidly by this ringing as a trigger, and an output of a short pulse width from the oscillator circuit is obtained as an output signal (see Non-Patent Literature 1).    Patent Literature 1: JP-A-2005-49200    Non-Patent Literature 1: T. Teshirogi, et al.: ‘Residual-carrier free burst oscillator for automotive UWB radar applications’, IEE2005 Electrics Letters 28 Apr. 2005 Vol. 41, No. 9